com.dimdim.conference.ui.json.client.ServerAvailabilityChecker.java Source code

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Here is the source code for com.dimdim.conference.ui.json.client.ServerAvailabilityChecker.java

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/*
 **************************************************************************
 *                                                                        *
 *               DDDDD   iii             DDDDD   iii                      *
 *               DD  DD      mm mm mmmm  DD  DD      mm mm mmmm           *
 *               DD   DD iii mmm  mm  mm DD   DD iii mmm  mm  mm          *
 *               DD   DD iii mmm  mm  mm DD   DD iii mmm  mm  mm          *
 *               DDDDDD  iii mmm  mm  mm DDDDDD  iii mmm  mm  mm          *
 *                                                                        *
 **************************************************************************
 **************************************************************************
 *                                                                        *
 * Part of the DimDim V 1.0 Codebase (http://www.dimdim.com)             *
 *                                                                        *
 * Copyright (c) 2006 Communiva Inc. All Rights Reserved.                 *
 *                                                                        *
 *                                                                        *
 * This code is licensed under the DimDim License                         *
 * For details please visit http://www.dimdim.com/license                 *
 *                                                                        *
 **************************************************************************
 */

package com.dimdim.conference.ui.json.client;

import com.google.gwt.user.client.HTTPRequest;
import com.google.gwt.user.client.ResponseTextHandler;
//import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.Timer;

/**
 * @author Jayant Pandit
 * @email Jayant.Pandit@communiva.com
 * 
 * As the name suggests, this class checks the server availability and
 * accessibility by using a given fixed url. The url must return a string
 * with non zero length. This string can be anything. It is not analyzed
 * by this class except to check its length.
 * 
 * The checker accepts the url, the timeout and the number of max failures
 * as parameters. It returns success on any valid return.
 */

public class ServerAvailabilityChecker {
    protected String url;
    protected ServerAvailabilityListener listener;
    protected int maxFailures;
    protected int waitTimeMillis;

    protected int numFailures = 0;
    protected Timer timer;
    protected ServerCheckerResponseTextHandler handler;

    private class ServerCheckerResponseTextHandler implements ResponseTextHandler {
        ServerAvailabilityChecker checker;

        public ServerCheckerResponseTextHandler(ServerAvailabilityChecker checker) {
            this.checker = checker;
        }

        public void onCompletion(String responseText) {
            //         Window.alert("Server Ping: response text: -"+responseText+"-");
            if (responseText != null && responseText.length() > 0) {
                //   Server is available. Call the appropriate method on the
                //   listener.
                checker.checkResult(true);
            } else {
                checker.checkResult(false);
            }
        }
    }

    public ServerAvailabilityChecker(String url, int maxFailures, int waitTimeMillis,
            ServerAvailabilityListener listener) {
        this.url = url;
        this.maxFailures = maxFailures;
        this.listener = listener;
        this.waitTimeMillis = waitTimeMillis;
        this.handler = new ServerCheckerResponseTextHandler(this);

        timer = new Timer() {
            public void run() {
                runCheck();
            }
        };
    }

    public void start() {
        this.timer.schedule(this.waitTimeMillis);
    }

    private void runCheck() {
        if (handler != null) {
            try {
                if (!HTTPRequest.asyncPost(url + "&cflag=" + (getClientGUID()), "a=b", handler)) {
                    //   Failure
                    checkResult(false);
                }
            } catch (Exception e) {
                //   Failure to contact the server. Increate
                checkResult(false);
            }
        }
    }

    private void checkResult(boolean success) {
        if (success) {
            if (this.listener != null) {
                this.listener.serverAvailable();
            } else {
                //   Nothing. No one to report to.
                //            Window.alert("No listener to report success to");
            }
        } else {
            this.numFailures++;
            if (this.numFailures >= this.maxFailures) {
                if (this.listener != null) {
                    this.listener.serverUnavailable();
                } else {
                    //   Nothing. No one to report to.
                    //               Window.alert("No listener to report failure to");
                }
            } else {
                //   Schedule the check again.
                this.timer.schedule(this.waitTimeMillis);
            }
        }
    }

    private native String getClientGUID() /*-{
                                          return ($wnd.getAGuid());
                                          }-*/;
}